The present invention relates to a mobile communication terminal device such as a portable telephone, a car telephone, a radio transceiver, or the like.
In recent years, with the higher speed of data communication, various applications of the mobile communication terminal device are thought about in addition to the application of sound communication as a basic function. As one of them, there may be listed a music broadcasting service. This music broadcasting service is provided to playback the digital audio music data, in that the digital audio music data stored in the CD (Compact Disk), etc., are broadcasted from the external source via the network, etc. and they are reproduced by the mobile communication terminal device. In order to meet such service, a new hardware must be added to the existing mobile communication terminal device.
In case a music playback function is added to the mobile communication terminal device, such mobile communication terminal device must be equipped with a sound communication function portion and a music playback function portion.
The sound communication function portion includes a pulse code modulation (abbreviated as xe2x80x9cPCMxe2x80x9d hereinafter) CODEC having an analog-to-digital (abbreviated as xe2x80x9cA/Dxe2x80x9d hereinafter) converter portion for converting a transmitting analog signal, which is transmitted, into a transmitting digital signal, and a digital-to-analog (abbreviated as xe2x80x9cD/Axe2x80x9d hereinafter) converter portion for converting a receiving digital signal, which is received, into a receiving analog signal.
While, the music playback function portion has a music playback function used in the CD player, etc., and includes an audio D/A converter for converting an audio digital signal, which is broadcasted, into an audio analog signal.
FIG. 9 shows a configuration of the existing mobile communication terminal device.
At the time of transmission, the transmitting analog signal, which is output from a microphone, is converted into the transmitting digital signal by an A/D converter constituting PCM-CODEC 203, and then transmitted via a TX (transmitter portion) 201 and an antenna 205.
At the time of reception, the receiving digital signal, which is received via the antenna 205, is converted into the receiving analog signal by a D/A converter constituting the PCM-CODEC 203 via an RX (receiver portion) 202, and then output as the receiving sound via a loudspeaker.
FIG. 10 shows a configuration of the mobile communication terminal device equipped with an audio D/A converter to meet the music broadcasting service.
At the time of transmission, the transmitting analog signal, which is output from the microphone, is converted into the transmitting digital signal by the A/D converter constituting the PCM-CODEC 203, and then transmitted via the TX (transmitter portion) 201 and the antenna 205.
At the time of reception, the receiving digital signal, which is received via the antenna 205, is converted into the receiving analog signal by the D/A converter constituting the PCM-CODEC 203 via the RX (receiver portion) 202, and then output as the receiving sound via the loudspeaker.
Meanwhile, audio digital signals containing the left channel (L-ch) and the right channel (R-ch), which are received via the antenna 205 based on the music broadcasting service, are converted into audio analog signals by an audio D/A converter 204 via the RX (receiver portion) 202, and then are output as audio sounds via the loudspeaker.
FIG. 11 shows a configuration of the PCM-CODEC 203 shown in FIG. 9 and FIG. 10.
The PCM-CODEC 203 includes an over-sampling type A/D converter 101 for converting the transmitting analog signal, which is output from the microphone, into the transmitting digital signal; an over-sampling type D/A converter 102 of the delta-sigma modulation system, for converting the receiving digital signal into the receiving analog signal to output it to the loudspeaker; a digital filter 105 for executing the decimation process of the A/D-converted transmitting digital signal; and a digital filter 106 for executing previously the interpolation process of the receiving digital signal to be D/A-converted.
It is normal that the PCM-CODEC 203 has a 8-bit data word length of the xcexc-law, but the CODEC which is extended up to 14 bit in place of the xcexc-law may be used according to the specification. The sampling frequency is 8 kHz.
FIG. 12 shows a configuration of the audio D/A converter 204.
The audio D/A converter 204 converts the audio digital signals containing the L-ch and the R-ch into analog signals, and includes digital filters 107, 108 for executing the interpolation process the L-ch and R-ch digital signals respectively, and over-sampling type D/A converter 103, 104 for converting the L-ch and R-ch digital signals, which have been subjected to the interpolation process, in the analog signal respectively.
The audio D/A converter 204 is employed in the digital audio such as CD, etc. The data word length is 16 bit (there is 24 bit in DVD (Digital Video Disk), etc.). The sampling frequency is 44.1 kHz in the CD, and is about 32 kHz to 48 kHz in other digital audio systems.
An operation of the PCM-CODEC 203 shown in FIG. 11 will be explained hereinafter.
At the time of transmission, the transmitting analog signal, which is output from the microphone, is converted into the transmitting digital signal by the over-sampling type A/D converter 101 by using the delta-sigma modulation system, then is input into a digital filter 105 to accept the decimation process, and then is sent out to the transmitter portion as the transmitting output.
As the over-sampling frequency, the sampling clock which is several tens to several hundreds times the sampling clock used in the A/D conversion of the normal sound signal, for example, is employed. In the portable telephone, etc., the sampling frequency of 8 kHz is standard for the sound and the over-sampling frequency of 1.024 MHz which is 128 times the sampling frequency, for example, is employed.
In the A/D converter 101 of such delta-sigma modulation system, the so-called noise shaping operation and the over-sampling operation are performed, and the output (noise shaping output) is a 1-bit signal which has been subjected to the PDM (Pulse Density Modulation). The 1-bit PDM bit stream output is down-sampled up to 8 kHz, which is the sampling frequency of the sound data, by the digital (decimation) filter 105 and is also converted into digital data of a predetermined bit number.
At the time of reception, the receiving digital signal, which is supplied from the outside as the receiving input, is over-sampled by the digital filter 106 to limit the bandwidth, and then input into the over-sampling type D/A converter 102. Here, the sound signal being converted into the receiving analog signal is supplied to the loud speaker and output as the telephone sound.
The digital filter 106 executes the quadruple over-sampling process and the bandwidth limiting process of the digital signal being input at the sampling frequency of 8 kHz. In addition, the digital filter 106 attenuates these fold-over frequency components simultaneously with the over-sampling process. Over-sampling data being processed by the digital filter 106 are input into the over-sampling type D/A converter 102 consisting of a noise shaper and an analog integration circuit, and then a 32-tuple over-sampling/ noise shaping process, for example, is applied to the data by the noise shaper to generate digital data as 1-bit stream data (compression waves generated by PDM). Also, this digital data is converted into the analog signal by the analog integration circuit by applying the integration process.
With the above, the operation of the PCM-CODEC 203 is explained. In this case, the digital filter 106 and the D/A converter 102 constituting the PCM-CODEC 203 and the audio D/A converter 103, 104 shown in FIG. 12 are different in the sampling frequency, the over-sampling rate, the circuit configuration according to the specification, etc., but they are similar in operation to each other. That is, the PCM-CODEC 203 shown in FIG. 11 and the audio D/A converter 204 shown in FIG. 12 are different in the data word length and the sampling frequency respectively, but they are common in that they execute the D/A conversion of the delta-sigma modulation system and the collaboration process made by the digital filter respectively. The circuit configurations for executing respective operations are differentiated based on the target specification and the difference in accuracy.
FIG. 13 shows a circuit configuration employed when the mobile communication terminal device picks up the music broadcasting service based on the PCM-CODEC 203 shown in FIG. 11 and the audio D/A converter 204 shown in FIG. 12. In this case, same symbols are affixed to parts similar to the parts shown in FIG. 11 and FIG. 12, and their detailed explanations will be omitted.
At the time of transmission, the transmitting analog signal being output from the microphone is converted into the transmitting digital signal by the A/D converter 101, then input in the digital filter 109 to accept the decimation process, and then output as the transmitting output.
At the time of reception, the receiving digital signal being supplied from the outside as the receiving input is input into the digital filter 109 to accept the interpolation process, then input into the D/A converter 102, and then converted into the receiving analog signal. After this, the analog signal is supplied to the loudspeaker and then output as the telephone sound. The digital filter 109 executes the decimation process and the interpolation process on time-division basis.
Meanwhile, the broadcasted L-ch and R-ch audio digital signals are input into the digital filter 110 respectively to accept the interpolation process, then input into the D/A converters 103, 104 to be converted into the analog signals, and then supplied to the loudspeaker. The digital filter 110 executes the interpolation process of the input audio digital signal for respective channels on time-division basis.
According to the above configuration, the user can listen to the L-ch and R-ch audio sounds while transmitting/ receiving the telephone sound.
However, there is such a problem that, since the configuration shown in FIG. 13 provides independently the speech (reception and transmission) process portion and the music sound playback portion, the power consumption is increased with the increase in the circuit scale.
As described above, the normal PCM-CODEC has the 8 kHz sampling and the 8-bit resolution. In this case, the circuit scale to achieve the 12 to 13 bit precision is needed because of the xcexc-law. In contrast, the audio D/A converter has the 44.1 kHz sampling and the 16-bit resolution.
The circuit scale is affected by the difference in the bit number. In case the audio D/A converter is added, the circuit scale is extended from about 14 bit to about 16 bit and therefore the circuit scale is increased by the increased bit number. In addition, since the configuration must respond to two channels of L-ch and R-ch, the circuit scale is increased at least two times the circuit scale of the PCM-CODEC only.
In contrast, since the audio D/A converter needs two channels, it needs two times the power consumption of the D/A converter portion of the PCM-CODEC. Also, since the sampling frequency is increased from 8 kHz to 44.1 kHz, i.e., about 5.5 times, the 5.5-times operation frequency is needed to execute the similar filter operation. Accordingly, the eleven-times (5.5 (sampling)xc3x972 (ch)=11) power consumption is needed in contrast to the power consumption necessary for the D/A conversion of the PCM-CODEC. Furthermore, the increase in the power consumption caused by the increase in the circuit scale based on the difference in the bit number is added.
According to the above results, it can be understood that, if the audio D/A converter is equipped to meet the music broad casting service, the circuit scale of the mobile communication terminal device is increased and also the power consumption is increased especially. The low power consumption is requested because it is premised on such an assumption that the mobile communication terminal device is operated by the battery. Under the circumstance that the existing mobile communication terminal device that is equipped only with the PCM-CODEC needs the considerable power consumption, it is impractical in a point of the power consumption to further equip the audio D/A converter.
The present invention has been made in view of such respects, and it is an object of the present invention to provide a mobile communication terminal device capable of reducing a circuit scale and reducing a power consumption upon meeting a music broadcasting service in addition to transmission/reception of a telephone sound.
In order to achieve the above object, in the mobile communication terminal device that is able to meet the new services such as the music broadcasting in addition to the transmission/reception of the telephone sound, the present invention takes account of the fact that the digital filters and the over-sampling type D/A converters existing commonly in the PCM-CODEC and the audio D/A converters constituting the terminal device can be used commonly, and thus makes it possible to reduce the circuit scale and reduce the power consumption by sharing the digital filters and the over-sampling type D/A converters and achieving the rationalization of the operation speed, the operation mode, etc.
A mobile communicating terminal device according to first aspect of the present invention comprises an A/D converter for converting a transmitting analog signal into a transmitting digital signal; a first selector for selecting any one of an output of the A/D converter and one channel of broadcasted audio digital signals; a second selector for selecting any one of a receiving digital signal and the other channel of the audio digital signals; a digital filter, to one input of which a first output of the first selector is supplied and to the other input of which a second output of the second selector is supplied, for applying a decimation process to the first output to send out to an outside if the first output is an output of the A/D converter, and for applying an interpolation process to the first output and applying the interpolation process to the second output if the first output is one channel of the audio digital signals, whereby the first output and the second output can be processed on time-division basis; a first D/A converter for converting one channel of the audio digital signals, which is subjected to the interpolation process by the digital filter, into an analog signal; and a second D/A converter for converting any one of the other channel of the audio digital signals and the receiving digital signal, which are subjected to the interpolation process by the digital filter, into the analog signal in synchronism with a selecting operation of the second selector.
A mobile communication terminal device according to second aspect of the invention comprises an A/D converter for converting a transmitting analog signal into a transmitting digital signal; a digital filter, to one input of which an output of the A/D converter is supplied and to the other input of which a receiving digital signal is supplied, for applying a decimation process to the output of the A/D converter to send out to an outside, and applying an interpolation process to the receiving digital signal, whereby the output of the A/D converter and the receiving digital signal can be processed on time-division basis; a selector for selecting any one of the receiving digital signal, which is subjected to the interpolation process by the digital filter, and one channel of broadcasted audio digital signals; a first D/A converter for converting any one of the receiving digital signal, which is subjected to the interpolation process by the digital filter, and one channel of the audio digital signals into an analog signal in synchronism with a selecting operation of the selector; and a second D/A converter for converting the other channel of the audio digital signals into the analog signal.
According to the above-mentioned first and second aspects, since the digital filters and the D/A converters can be used commonly, not only the circuit scale can be reduced but also the power consumption can be reduced.
A mobile communication terminal device according to third aspect of the invention comprises an A/D converter for converting transmitting analog signal into a transmitting digital signal; first digital filter for applying a decimation process to an output of the A/D converter to send out to an outside; a second digital filter, to one input of which a receiving digital signal or one channel of broadcasted audio digital signals is supplied and to the other input of which the other channel of the audio digital signals is supplied, for applying an interpolation process to the receiving digital signal or one channel of the audio digital signals, and for applying the interpolation process to the other channel of the audio digital signals, whereby the receiving digital signal or one channel of the audio digital signals and the other channel of the audio digital signals can be processed on time-division basis; a first D/A converter for converting the receiving digital signal or one channel of the audio digital signals, which is subjected to the interpolation process by the second digital filter, into an analog signal; and a second D/A converter for converting the other channel of the audio digital signals, which is subjected to the interpolation process by the second digital filter, into the analog signal.
A mobile communication terminal device according to fourth aspect of the invention comprises an A/D converter for converting a transmitting analog signal into a transmitting digital signal; a first digital filter, to one input of which an output of the A/D converter is supplied and to the other input of which a receiving digital signal or one channel of broadcasted audio digital signals is supplied, for applying a decimation process to the output of the A/D converter to send out to an outside, and for applying an interpolation process to the receiving digital signal or one channel of the audio digital signals, whereby the output of the A/D converter and the receiving digital signal or one channel of the audio digital signals can be processed on time- division basis; a second digital filter for applying the interpolation process to the other channel of the audio digital signals; a first D/A converter for converting the receiving digital signal or one channel of the audio digital signals, which is subjected to the interpolation process by the first digital filter, into an analog signal; and a second D/A converter for converting the other channel of the audio digital signals, which is subjected to the interpolation process by the second digital filter, into the analog signal.
A mobile communication terminal device according to fifth aspect of the invention comprises an A/D converter for converting a transmitting analog signal into a transmitting digital signal; a first digital filter, to one input of which an output of the A/D converter is supplied and to the other input of which a receiving digital signal is supplied, for applying a decimation process to the output of the A/D converter to send out to an outside and applying an interpolation process to the receiving digital signal, whereby the output of the A/D converter and the receiving digital signal can be processed on time-division basis; a second digital filter to which both channels of broadcasted audio digital signals are supplied, for applying the interpolation process to both channels of the audio digital signals on time-division basis; a selector for selecting any one of the receiving digital signal, which is subjected to the interpolation process by the first digital filter, and one channel of the audio digital signals, which is subjected to the interpolation process by the second digital filter; a first D/A converter for converting any one of the receiving digital signal, which is subjected to the interpolation process by the first digital filter, and one channel of the audio digital signals, which is subjected to the interpolation process by the second digital filter, into an analog signal in synchronism with a selecting operation of the selector; and a second D/A converter for converting the other channel of the audio digital signals, which is subjected to the interpolation process by the second digital filter, into the analog signal.
According to the above-mentioned third, fourth and fifth aspects of the invention, since the D/A converters can be used commonly, not only the circuit scale can be reduced but also the power consumption can be reduced.
A mobile communication terminal device according to sixth aspect of the invention comprises an A/D converter for converting a transmitting analog signal into a transmitting digital signal; a selector for selecting any one of an output of the A/D converter and a receiving digital signal; a first digital filter to which an output of the selector is supplied, for applying a decimation process to the output of the A/D converter to send out to an outside if the output of the selector is an output of the A/D converter, and for applying an interpolation process to the receiving digital signal if the output of the selector is the receiving digital signal; a second digital filter to which both channels of audio digital signals are supplied, for applying the interpolation process to both channels of the audio digital signals on time-division basis; a first D/A converter for converting the receiving digital signal, which is subjected to the interpolation process by the first digital filter, into an analog signal; a second D/A converter for converting one channel of the audio digital signals, which is subjected to the interpolation process by the second digital filter, into the analog signal; and a third D/A converter for converting the other channel of the audio digital signals, which is subjected to the interpolation process by the second digital filter, into the analog signal.
A mobile communication terminal device according to seventh aspect of the invention comprises an A/D converter for converting a transmitting analog signal into a transmitting digital signal; a selector for selecting any one of an output of the A/D converter and a receiving digital signal; a first digital filter, to one input of which an output of the selector is supplied and to the other input of which one channel of broadcasted audio digital signals is supplied, for applying a decimation process to the output of the A/D converter to send out to an outside if the output of the selector is the output of the A/D converter, and for applying an interpolation process to the receiving digital signal and applying the interpolation process to one channel of the audio digital signals if the output of the selector is the receiving digital signal, whereby the output of the selector and one channel of the audio digital signals can be processed on time-division basis; a second digital filter for applying the interpolation process to the other channel of the audio digital signals; a first D/A converter for converting the receiving digital signal, which is subjected to the interpolation process by the first digital filter, into an analog signal; a second D/A converter for converting one channel of the audio digital signals, which is subjected to the interpolation process by the first digital filter, into the analog signal; and a third D/A converter for converting the other channel of the audio digital signals, which is subjected to the interpolation process by the second digital filter, into the analog signal.
According to the above-mentioned sixth and seventh aspects of the invention, since the 1-input/output type digital filter that is not operated on time-division basis is employed, there is no necessity to increase the operation speed and therefore the power consumption can be reduced.